NDLI: Factor cuts

Content Provider	ACM Digital Library
Author	Mishchenko, Alan Brayton, Robert Chatterjee, Satrajit
Abstract	Enumeration of bounded size cuts is an important step in several logic synthesis algorithms such as technology mapping and re-writing. The standard algorithm does not scale beyond 6 or 7 inputs because it enumerates all cuts and there are too many of them. We address the enumeration problem by introducing the notion of cut factorization. In cut factorization, one enumerates global and local cuts (collectively called the factor cuts) of the network, and uses these to generate other cuts. Depending on how global and local cuts are defined, one obtains different factorization schemes. In the first scheme, complete factorization, it is possible to generate any cut from factor cuts. However, complete factorization is expensive though less expensive than exhaustive enumeration. In the second scheme, partial factorization, there is no guarantee of generating all cuts from factor cuts. However, it is much faster, and produces good results. In this paper we also present two applications of factor cuts: LUT mapping and macrocell mapping. In LUT mapping, we find that considering only factor cuts guarantees depth optimality for most nodes in the network. For the remaining nodes, other cuts need to be generated from factor cuts and examined. In macrocell mapping, we focus on a particular 9-input macrocell, and use factor cuts as a heuristic method to improve depth by reducing structural bias. Factor cuts are used to map the macrocell as a whole whenever possible instead of mapping its parts separately. In this context factor cuts enable a new quality-run-time tradeoff between mapping parts of the macrocell separately (poor quality), and mapping using all 9-input cuts (long run-time).
Starting Page	143
Ending Page	150
Page Count	8
File Format	PDF
ISBN	1595933891
ISSN	10923152
DOI	10.1145/1233501.1233531
Language	English
Publisher	Association for Computing Machinery (ACM)
Publisher Date	2006-11-05
Publisher Place	New York
Access Restriction	Subscribed
Content Type	Text
Resource Type	Article
Subject	Computer Graphics and Computer-Aided Design Software Computer Science Applications

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